[heap] Remove two DCHECKs for minor concurrent marking

This CL removes two DCHECKs which no longer hold with minor
concurrent marking.

Bug: v8:13012
Change-Id: I6f24284f0955c57deeb2fa2c300623d9aedfdd3c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3865463Reviewed-by: Omer Katz <omerkatz@chromium.org>
Commit-Queue: Leon Bettscheider <bettscheider@google.com>
Cr-Commit-Position: refs/heads/main@{#82890}

src/heap/mark-compact.cc

@@ -5528,9 +5528,6 @@ class YoungGenerationEvacuationVerifier : public EvacuationVerifier {
 
 bool IsUnmarkedObjectForYoungGeneration(Heap* heap, FullObjectSlot p) {
   DCHECK_IMPLIES(Heap::InYoungGeneration(*p), Heap::InToPage(*p));
-  DCHECK(
-      !heap->minor_mark_compact_collector()->non_atomic_marking_state()->IsGrey(
-          HeapObject::cast(*p)));
   return Heap::InYoungGeneration(*p) && !heap->minor_mark_compact_collector()
                                              ->non_atomic_marking_state()
                                              ->IsBlack(HeapObject::cast(*p));
@@ -5589,7 +5586,6 @@ void MinorMarkCompactCollector::CleanupPromotedPages() {
 }
 
 void MinorMarkCompactCollector::VisitObject(HeapObject obj) {
-  DCHECK(marking_state_.IsGrey(obj));
   main_marking_visitor_->Visit(obj.map(), obj);
 }